Editor's note: In this five-part series, Government Technology examines the present impact of technology on transit systems and what that can mean for the future of urban transportation.

Transit riders love using their smartphone to purchase rides. But just a few agencies have embraced the technology so far.

In 2013, Americans took 10.7 billion trips on public transit, the highest number in 57 years, according to the American Public Transportation Association. For decades the demographic profile for the typical transit rider was someone who was low income and often had no other means of transportation. In other words, people who used public transit did so because they had to, not because they wanted to.

But since 1995, public transportation ridership has grown 37.2 percent, almost double the amount of the country’s population growth at 20.3 percent, according to APTA. Clearly a new generation of transit riders has stepped forward. Many of them are so-called “choice riders” who have other options to get around besides buses and trains, but prefer using public transit. To keep these choice riders coming back, experts say that transit agencies must offer a ride that is reliable, fast and clean. They also want convenience.

One way that transit agencies can make the daily commute convenient for riders is with mobile ticketing. With approximately 91 percent of adults using a cellphone, according to Pew Research, the push to collect fares via an app on a mobile phone is extremely appealing to transit agencies. Not only does the technology make it easy for people to purchase rides, but mobile ticketing also lowers the cost of fare collection because riders pay for the fare equipment — the mobile phone — not the agency. In a 2013 Accenture survey of transit riders in nine major cities, more than half of respondents said they would be willing to pay more per ride for tech enhancements like paperless ticketing, and 75 percent said travel would be easier with electronic ticketing.

In 2013, Dallas Area Rapid Transit launched one of the first mobile phone fare collection systems in the country. Technology for the system was developed by the Danish firm Unwire, which has extensive experience with mobile ticketing in Europe. In the same year, TriMet also unveiled the first mobile ticket for use on both buses and trains. A year later, the agency sold nearly 1 million mobile tickets, surpassing expectations. “Our mobile ticketing app has been an overwhelming success, quickly surpassing our expectations,” said TriMet General Manager Neil McFarlane in a release.

Prior to launching the service, TriMet knew that 50 percent of its riders had a smartphone; today the number is closer to 60 percent, according to Chris Tucker, TriMet’s director of revenue operations. Mobile ticketing allows riders to buy tickets anytime, anywhere. “We’re seeing a big shift in how riders purchase fare tickets,” said Tucker. “Fewer are heading to retail stores or a ticket vending machine to buy their ticket.”

The current version of the mobile ticketing system is a stand-alone system that operates in conjunction with the agency’s legacy fare collection system. But TriMet is developing a new, comprehensive fare collection system that, when finished, will allow the agency to get rid of aging and expensive fare collection equipment and reduce the cost of fare collections as a percentage of revenue. Mobile ticketing will be a fully integrated feature. GlobeSherpa, an Oregon-based mobile payment and ticketing company, is helping TriMet develop the digital fare system.

Not surprisingly, other agencies are moving in this direction. Long Island Rail Road, the nation’s largest commuter rail system, expects up to 25 percent of its riders to use its yet-to-be-launched mobile ticketing app within five years. The Massachusetts Bay Transportation Authority rolled out a mobile ticketing service for commuter rail riders in 2012. Both ticketing systems were developed by Masabi, another mobile ticketing software company.

But mobile ticketing isn’t just a convenience for riders. To keep mobile ticketing attractive to riders, and to entice new riders to use TriMet’s transit services, the agency plans to offer a discount system in the form of fare caps, which will allow passengers to ride for free once they’ve used the full value of the fares they have purchased. Tucker compared the fare cap system to a retail gift card, but with discounts built in. “This is going to be exciting for everyone, because it will be much easier to use,” he said. “It really frees up the options riders have as to how they plan their journey.”Next: Look for "Intelligent Transit: Data Improves Transit Efficiency" on March 27.

With more than 20 years of experience covering state and local government, Tod previously was the editor of Public CIO, e.Republic’s award-winning publication for information technology executives in the public sector. He is now a senior editor for Government Technology.